1. Field of the Invention
The present invention relates generally to the field of motion picture production systems, and more particularly, to an improved apparatus for positioning a camera for motion picture photography.
2. Description of the Related Art
Special effects have played an important role in motion picture productions since the early days of the film industry. In recent years, numerous box office hits testify to the captivating power of special effects, and underscore the significance of special effects in contemporary film making. With each new motion picture production, the film makers are pushing the envelope to out do the last production in special effects. State of the art digital technologies have become a significantly part of special effects. For example, the quality of an image obtained by composite photography may be significantly improved by using digital processes in putting together the image.
While modern digital technologies may allow compositing two or more image elements in a seamless manner to create a stunning visual effect with a realistic xe2x80x9cfeelxe2x80x9d, there are times when there is no substitution for the real expressions and movements of the actors. For example, for an action scene in which it is intended to show a lion pursuing and ferociously tackling a man to the ground, the lion does not have to be taught its natural terrifying behavior and it would be counter productive for anyone to try to teach the lion to act any differently against its nature. For obvious safety reasons, the action sequence for the lion must be filmed separately from that of its victim. The two action sequences may then be digitally composited in the film studio to create the deadly encounter on screen. Given that successful compositing requires elements of the scene to be perfectly matched, the proper positioning of the camera is important to accomplish this end. It has been a challenge to ensure that this can be accomplish with the separate camera takes.
In the past, movie cameras have been mounted on dollies which are provided with wheels, which move on the ground or along tracks having two parallel rails. The dollies may be pushed along the tracks during filming, or they may be self-propelled. While the prior art dollies allow easy movement and positioning of the cameras, they were not satisfactory in ensuring precise and repeatable camera positioning for composite shots. Further, the movement of the prior art dollies were accompanied by vibrations and noise, which are undesirable to filming. These undesirable effects are more pronounced when the dollies negotiate turns along curve section of the tracks. For example, the model xe2x80x9cSuper Pantherxe2x80x9d dolly made by Panther of Germany and distributed by Shopmaker Company was found to be unacceptable for filming scenes in which it is critical to minimize vibrations and noise. Furthermore, the structure of the Panther dollies was found to deflect under the weight of the camera gear, to an extent as to be unacceptable for precision positioning of the camera.
The present invention is directed to an improved self-propelled camera positioning device (hereinafter referred to as a xe2x80x9cdollyxe2x80x9d) which is configured to minimize noise and vibration during its movement on a track. The dolly rides on a track which comprises three rails, with the drive wheels of the dolly riding on the center rail. In a preferred embodiment, the dolly comprises a camera support unit and a drive unit which are coupled by a flexible coupling. The flexible coupling comprises segments coupled by three hinges at a horizontal axis and two vertical axes, thereby allowing the coupling freedom to flex. The support unit is designed with outer wheels which run along a pair of parallel rails of the track. The drive unit has a set of drive rollers which run along a center rail between the two outer rails of the track, thereby pulling and pushing the support unit along the track. One of the drive rollers is powered by a motor, which is controlled by a programmable controller. In a specific embodiment of the present invention, a pinch mechanism biases the drive wheels against the sides of the center rail. All the wheels and rollers on the dolly are provided with a resilient rolling surface.
The structure of the dolly is configured to minimize any undesirable structural deflections under the load of the camera gear. The flexible coupling is designed with no free play in the hinges. The dolly is designed to be disassembled into several pieces for ease of shipping and reassembled without the use of separate hand tools. Quick detach couplings are implemented for coupling the pieces of the dolly.
In another aspect of the present invention, the controller is programmed through the movement of the dolly. The controller memorizes the movement of the dolly so that such movement may be repeated with precision to reposition the camera to retake the scene or to go through precisely the same camera motions with a different scene element for compositing an image.